It is known that communication networks allow to provide users with a number of data services (for instance, Internet access, e-mail, exchange of messages, video-on-demand) and/or telephone services (for instance, calls and conference calls).
A user may access such services by means of a terminal, which can be either a fixed terminal (i.e. a terminal which is connected to the communication network distributing the services through a wired connection) or a mobile terminal (i.e. a terminal which is connected to the communication network distributing the services through a wireless connection). Exemplary mobile terminals are the GSM (Global System for Mobile communications) or UMTS (Universal Mobile Telecommunication System) mobiles and the laptop computers provided with a GSM or UMTS interface, or with a Bluetooth or Wi-Fi interface.
A terminal (in particular, a mobile terminal) is frequently equipped with a number of sensors allowing to detect context information about the terminal. In the following description and in the claims, the expression “context information about a terminal” will designate a set of information indicative of the context (i.e. the environment and/or the operating status) in which the terminal is put. Exemplary context information are:                the terrestrial coordinates at which the terminal is located, which may be detected e.g. by a GPS device installed on the terminal;        the identifier of the mobile cell the device is connected to, which may be detected by any GSM or UMTS mobile;        the luminosity and/or the temperature and/or the humidity of the environment surrounding the terminal, which can be detected by suitable sensors installed on the terminal;        the acceleration to which the terminal is subjected, which can be detected by an accelerometer installed on the terminal;        the presence of a Wi-Fi hotspot in the environment surrounding the terminal, which can be detected by a Wi-Fi interface installed on the terminal; and        the presence of Bluetooth devices in the environment surrounding the terminal, which can be detected by a Bluetooth interface installed on the terminal.        
Service providers are able to collect context information from the terminals of their users, and to process them for providing data services and telephone services which are capable of adapting themselves to the context of the terminals. In the following description and in the claims, the expression “context-based service” will designate a data service or a telephone service which is capable of acquiring context information from a terminal and to use such context information for adapting itself to the context of the terminal.
U.S. Pat. No. 7,383,253 discloses a Continuous Query Processor that processes queries on continuously updating data sources or data streams and includes a Publication Manager for accepting published structured elements of data from data stream Publishers, a Subscription Manager for giving structured elements of data to one or more data stream Subscribers, a Query Module Manager for processing queries represented by Query Modules, a Query Module Store for maintaining deployed Query Modules, a Query Primitive Manager performing processing for various primitives that comprise a Query Module, and a Schedule Manager for coordinating when a primitive within a Query Module gets processed in order to maintain that each continuous query is continuously updated immediately upon the arrival of structured element data affecting any part of a continuous query.
US 2005/071322 discloses a concept called virtual construct intervals (VCI), where each predicate interval is decomposed into one or more of these construct intervals. These VCIs strictly cover the predicate interval. Namely, every attribute value covered by the predicate interval is also covered by at least one of the decomposed VCIs, and vice versa. Each construct interval has a unique ID or interval coordinate and a set of endpoints. A construct interval is considered activated when a predicate interval using it in its decomposition is added to the system. The predicate ID is then inserted into the ID lists associated with the decomposed VCIs. To facilitate fast search, a bitmap vector is used to indicate the activation of VCIs that cover an event value. The challenge is to find an appropriate set of construct intervals to make predicate decomposition simple and, more importantly, to build efficient bitmap indexes. Because each construct interval covers only a small range of attribute values, the invention also uses bitmap clipping to cut unnecessary bitmap storage. To facilitate bitmap clipping, the invention introduce the covering segment concept. Bit positions outside a covering segment are pruned.
US 2004/267769 discloses a systems and methods to increase the scalability of subscriptions in an electronic database environment. In an illustrative implementation, a computing application comprises at least one instruction set to cooperate with a data environment to optimise the processing of subscriptions by the data environment when communicating with cooperating services and/or applications. In operation, a subscription is identified. A subscription template is created for the subscription and the subscription template is parameterised to create a parameter table containing parameters (e.g. subscription constants). A join is then performed between the parameters of the parameter table and the parameterised subscription templates to generate application and/or service data required by the cooperating services and/or applications. The data is then processed by the applications and/or services.